Temperature sensors and thermostats are used in a variety of heating, ventilation, and air conditioner (HVAC) systems, as well as in dryers and furnaces. For instance, in industrial paint dryers, a painted object is set inside the dryer for a period of time to rapidly cure the paint. In such devices, a proper control on the temperature around the object significantly affects its final quality. If the drying rate is too fast, the paint will crack and if it is too slow, it will take a longer time to dry, reducing the productivity. Moreover, if the temperature distribution around the object is not even, some spots may remain wet after the operation.
Almost all thermostats use a single temperature sensor at one location to control the temperature of the indoor space (hereinafter, referred to “conventional thermostat”). The disadvantage of a conventional thermostat is that only local temperature around the temperature sensor is controlled. Generally, there is no control on the temperature in locations far from the temperature sensor. FIG. 1 shows the lay down of a conventional thermostat 130 located between the inlet 120 and air outlet 140 to control the temperature in the space 150 with a person 111 in the middle of the space. The target temperature location 110 is around the person. In the conventional thermostat, the user set the temperature to certain level for HVAC system to operate based on (with the assumption of well mixed air condition inside the controlled space). However, the temperature distribution of the air is not well mixed as can be seen in FIG. 2-A and FIG. 2-B (where they show temperature distribution around person in middle of a room with heating system). Air circulation has strong effect on temperature distribution inside the controlled space. The circulation of the air depends on the fan power and direction, and the geometry of the space being controlled. However, the HVAC inlet layout and design are not the only factors to maintain the desired environment on the targeted zone. The location of the temperature sensor represents the targeted zone temperature, which can be very different than the location of interest. This lack of ability to measure the condition of the targeted location relatively far from the thermostat results that conventional thermostat over- or under-estimates the temperature of the targeted location. FIG. 3 compares average temperature around a conventional thermostat and average temperature around a person for an HVAC system. The HVAC system is heating the space to keep the temperature between 25° C. and 24° C. In addition, the HVAC system is turned ON and OFF based on a feedback from the conventional thermostat. Therefore, whenever the temperature around the sensor gets to 25° C. the system turns OFF and turns ON when temperature drops to 24° C. However, because of the distance, the local temperature around the person is over- and under-estimated. The problem of a single point measurement is not just related to temperature measurement but also can be generalized to any single point sensor like humidity sensor, or air velocity sensor.
Human thermal comfort is related to several factors such as temperature, humidity, air velocity. Hence, a better and more efficient HVAC system can be designed, if such factors are better controlled. Improper control of the air temperature reduces the energy efficiency of a HVAC system by more than 40%. In addition to poor energy efficiency, improper temperature control reduces indoor thermal comfort, and may result in other issues depending on the particular application, such as inadequate drying of objects in dryers.
The main object of the present invention is to control the temperature of a particular location or zone, instead of using a single point measuring sensor far away from the targeted location. Since it is not feasible to put temperature sensors throughout the whole space, the temperature control is achieved by simulating the air behavior inside the controlled space. The result is like having number of movable single point measuring sensors inside a specified location, instead of a single temperature measure far away from the interest zone. A computational fluid numerical solver is used to determine air behavior inside the controlled space. This information can be used to estimate the average condition (for example average temperature) around the targeted location. As a result, the average condition can be used to determine when to turn ON and OFF the HVAC system.